Disease* Triggered by trauma or infection, sepsis can lead to organ failure and death, particularly among those with weak immune systems.

On any given day in the medical intensive care unit at Yale-New Haven Hospital in Connecticut, three or four of the 14 beds are occupied by patients whose own bodies threaten to kill them before their disease does.

They are the victims of sepsis, an overwhelming immune response to infection or trauma that can plow through the body like a freight train, shutting down lungs, kidneys and heart. Across the country this year, an estimated 225,000 people will die of sepsis.

"Eighty percent of sepsis patients have something else wrong with them, but anybody can get this," said Dr. Mark D. Siegel, director of the medical intensive care unit at Yale-New Haven. "From the time it starts, a patient who is immuno-suppressed from AIDS or cancer could be dead in a matter of hours."

In the last decade, the medical community has become more adept at recognizing and preventing the devastating series of events that leads to severe sepsis, which used to kill more than 60% of its victims. But about one-third of people who become septic still are expected to die.

Though the death rate in severe cases has been cut nearly in half in recent years, some experts expect the death toll from sepsis--already larger than breast, prostate and colon cancers combined--will continue to rise.

A study by Emory University and the Centers for Disease Control and Prevention showed that the incidence of sepsis more than tripled between 1979 and 1999, increasing by an average of 16% each year. In that 20-year period, the number of cases rose from 78 per 100,000 people to 259. Experts say that is primarily because more and more elderly patients with frail immune systems have been treated with life-saving techniques, such as chemotherapy and intensive care ventilators, that also carry a risk of a potentially sepsis-triggering infection.

"I'm not optimistic we can reduce that number," said Dr. Gordon Bernard, professor of medicine at Vanderbilt University Medical School and chief of pulmonary and critical care at Vanderbilt Hospital.

That doesn't mean there aren't things that can't be done, he said.

Elderly people, for instance, can remain current with vaccinations for flu and pneumococcal pneumonia. Hospitals can reduce the risk of infection by simply making sure that nurses and doctors keep their hands washed, Bernard said.

"It's like a turn signal," Bernard said. "You should do it 100% of the time, but sometimes you don't."

Also, doctors and hospital staff need to learn more about sepsis and recognize the symptoms of its onset, he said.

In the early stages, sepsis can be mistaken for a low-grade illness. Patients might have a low fever. The difference is that with sepsis the heart and breathing rates might be unusually rapid. Blood tests will show white blood cell counts that are unusually high or low.

Antibiotic treatment of the underlying infection must be prompt to prevent events that lead to widespread organ failure, doctors say.